Having owned two previous Rams (2009 4x2 Laramie and 2014 4x4 Laramie Longhorn), I was partial to Ram when my current shopping experience started. I will have to say I have enjoyed reading the posts but I thought I would add my comments to this as I too am currently deciding between the Ram and the Sierra and my aspects are different than the OP because I'm looking at a different trim level.
71555 (1500 rebates)
Ram Limited: $71,555 MSRP (4x4, eTorque, Anti=Spin, 3.92, 33-gallon, Limited Level-1, Body-Color Group, Bed Utility Group, 22s, MFT, RamBox, DualPane, Trailer Brake)
Ram rebates: $1500 or 0.9/84mo or 0.0/72mo
Sierra AT4: $66,940 (4x4, 3.0L Duramax Diesel, AT4 CarbonPro Package, Technology Package, AT4 Premium Package, AT4 Preferred Package, Driver Alert I Package, Driver Alert II Package, Cargo Convenience Package, 20" Carbon Grey Wheels and Sunroof)
Sierra Denali: $72,235 (4x4, 3.0L Duramax Diesel, Denali CarbonPro which includes all AT4 packages, GMC Protection Package)
Looking at this I'm sure it seems like an odd comparison but here's how I arrived at these final two contenders. For Ram, I had to immediately rule out the EcoDiesel because it costs $3K more and with Diesel in the US averaging between 40-60 cents more per gallon than unleaded, I'll never break even. I did tons of analysis varying mileage, and increasing gas costs but it won't happen so absolutely zero point and that doesn't even take into account the additional maintenance (DEF, fuel filter changes, more expensive oil changes, etc.). That meant for Ram, I was going to go with the eTorque.
For GMC, it's a no brainer to choose the Duramax. The 5.3L is a dog in the Sierra as I test drove the 5.3L, 6.2L and the 3.0 Duramax. The upgrade cost for the 6.2L V8 and the 3.0L Duramax is the same ($2,495 on the AT4) but the 6.2L has an EPA combined rating of 17 and requires premium gas whereas the 3.0L Duramax has an EPA combined rating of 24. Because the upgrade cost is the same, I'm saving gas immediately even at these low gas prices ($1.31 for unleaded here and $1.86 for diesel). The 6.2L and 3.0L Duramax both really move and the Duramax didn't have the turbo lag that the EcoDiesel had. The 6.2L was a touch faster off the line but not a huge difference at all.
The reason I didn't use a Denali is this (I did test drive a Denali as well) is because the Denali would cost $5,295 and the only difference is the adaptive ride suspension that the AT4 doesn't have, honeycomb chrome grill, chrome chin, chrome tow hooks, chrome window surround trim, power running boards and 22" wheels. That's it. I couldn't see spending that much more for just those differences. The AT4 gets you a factory 2" Lift, bigger tires, still get 20" wheels, offroad upgraded suspension, contrast brown stitching interior with Kalahari accents (brown) in the seats, etc.
As far as ride is compared, the Denali, AT4 and Ram with air suspension were all smooth trucks. I drove them on the highway, side streets, speed bumps, and honestly couldn't decipher a really noticeable difference as that is what I was concerned with in particular with the AT4. The CarbonPro is really nice because it's a carbon fiber bed that is indestructible and weights 60+lbs less increasing payload, towing and of course reducing weight so that should help with fuel economy.
Now for real world pricing. The best deal I have seen on a Limited is Koon's 15.5% off MSRP but within driving distance of me (500 miles or less) I've seen about 12.58%. That means a Limited stickering at $71,555 would cost me $62,555 BEFORE rebates or financing. AT4s are hard to find but I have a supplier pricing code that gurantees invoice right now if I wanted to pull the trigger at $62,365.11 BEFORE $7500 in rebates or 0.0/84mo. If I went rebates, the Ram would cost me $60,055 before TT&L and the AT4 would cost me $54,865.11 before TT&L. Obviously if I chose financing the AT4 would be a little over $30/mo cheaper as well and I wouldn't get rebates.
Comparisons: The Ram interior is absolutely better. The Sierra's is better IMO than Tundra, Ford and Titan but Ram is in a class by itself.. The Ram would get me a better interior and RamBoxes. The AT4 would get me a lift, heads-up display, way more cameras including bedview and rearview mirror, diesel, save gas, better looking on the outside, GMCs tailgate with soundsystem included in the tailgate, etc. As you can see, the list of equipment advantages of the Sierra AT4 exceed the Ram Limited but that interior and those ramboxes..haha. I've been following the problems plauging the Ram and I know forums always magnify the problems potentially but I was lucky in that my two Rams I owned (total of little over 130,000 miles) I never saw any issues. I don't know how reliabiltly is with GMC Sierra's. Anyway, I'll conclude my novel and comparison but I'm trying to decide as well.